Carburetor



April 6, 1943. w. E. LEIBING- ETAL CARBURETOR Filed May 1, 1941 3Sheets-Sheet l m m Z W Wm W M ,0 m WR mm 0, i M 6% w. 0v m 2 WW mm m m6mm 8 ad A ril 6, 1943.. w. E. LEIBING ETAL 2,315,717

. CARBURE'IOR 4 Filed May 1, 1941 '3 Sheets-Sheet 2 n we n ow 4 1mm,flawalaiww M2 du-ouw April w. E. LEIBING ETAL 2,315,717

GARBURETOR Filed May 1, 1941 3 Sheets-Sheet 3 kallgfl. 159ml PatentedApr. 6, 1943 UNITED STATES PATENT OFFICE CAR-BURETOR William E. Leibing,San Rafael, Calif., and Robley D. Fageol, Grosse Pointe Farms, Mich,assignors to Leibing-Fageol Company, Detroit, Mich.,

a partnership composed of F.

R. Fageol,

Application May 1, 1941, Serial No. 391,412

Claims.

The present invention relates to improvements in carburetors forinternal combustion engines, and more particularly to that class ofcarburetors in which the throttle valve for controlling the flowsthrough the fuel conduit is positioned on the atmospheric side, orup-stream side, of the jet, or jets, feeding the fuel into the conduit,such a carburetor being sometimes known as the anterior throttle type.However, it is to be understood that a number of the features disclosedherein are applicable as well to carburetors of any type.

The present invention is intended as an improvement over the carburetordisclosed in application Serial No. 359,282, filed October 1, 1940,having as a major object the provision of a metering means of novelconstruction for'supplying fuel to a single jet in the carburetor fornormal running conditions of the engine, includ ing idling, thuseliminating the necessity for a special idling jet with its attendantfuel supply and adjustment means.

A further object of my invention is the provision of a novel fuelmetering means for a carburetor wherein a fuel metering arm within afuel chamber is provided to move in accordance with the throttle valveshaft, the connection of the arm and the shaft being protected againstthe access of fuel thereto under normal running conditions withconsequent leakage of excess fuel into the carburetor conduit.

A further object of the present invention is to provide novel fuelmetering means wherein the size of the fuel metering opening, oropenings, can be readily varied to adapt the metering means to differentengines and different conditions of operation at different throttlepositions without expensive machinery or material alteration of anyparts.

Still a further object of this invention is the provision of acarburetor having novel metering means adapted to be variably immersedin the fuel in the float chamber of the carburetor, means being providedto eliminate the effect of variations in the fuel level in said chamberand provide ready means to vary the air fuel ratio developed by themetering means.

A further object of the invention is the provision of a carburetorhaving novel fuel metering means wherein the effect of tips, angles, andsurge within the float chamber are eliminated to an extent whereby thecarburetor is capable of satisfactory use on cross-country vehicles suchas tanks, tractors, trucks, reconnaissance cars, and like militaryvehicles.

Still a further object of the invention is the provision of a novelcarburetor wherein by the substitution of throttles of differentangularitles when in closed position, considerable change in throttleprogression can be effected, means being also provided in thesubstitution of relatively simple and inexpensive elements to change theair fuel ratio relative to various positions of the carburetor throttle.

A further object of the invention is the provision of a novel method ofvarying the character of the fuel mixture developed by a carburetorwhich includes the step of correlating the angularity of the throttlevalve to the fuel metering means to predetermine the rate of effectiveopening through the carburetor conduit corresponding to the movement ofthe metering means by the throttle valve.

A further object of the invention is to provide a novel method ofvarying the fuel mixture developed by a carburetor having slottedmetering means arranged to be progressively immersed in liquid fuelwhich comprises the step of sealing the slot in the metering means fromthe liquid fuel at the fuel level line and varying the length of saidsealing means to vary the length of the metering slot sealed by thesealing means.

Still a further object of the invention is the provision of a novelmethod of varying the fuel mixture developed by a carburetor havingslotted metering means arranged to be progressively immersed into liquidfuel by varying the effective opening of said slot at pointscorresponding to predetermined positions of the throttle valve.

Other objects and advantages of the present invention will appear fromthe following description and claims, including the appended drawings,wherein Figure 1 is a side elevation, partly in section, of a preferredembodiment of the present invention in a carburetor of the anteriorthrottle down-draft type taken on the line i-l of Fig ure 4.

Figure 2 is a section taken on the line 2-2 of Figure 4, looking in thedirection of the arrows.

Figure 3 is a section taken on the line 3-3 of Figure 1.

Figure 4 is a plan of the carburetor as it appears in Figure 3.

Figure 5 is a side elevation looking from the right of Figure 4, withcertain control connections added.

Figure 6 is a longitudinal section on an enlarged scale of the meteringarm of Figure l.

Figure 7 is a section taken on the line l-l of Figure 6, with a portionof the throttle valve shaft added.

Figure 8 is a perspective of the assembly shown at the upper lefthandcorner of Figure 1.

Figure 9 is a section taken through the gasket of the metering arm ofFigure l with a modified type of adjustment and control means shown incombination therewith.

Figure 10 is an elevation of the adjustment block of Figure 9 asreviewed from the right of that figure.

Figure 11 is a plan view of the adjustment block and a portion of themetering arm viewed in the direction of the arrow in Figure 9.

The present invention is described for the purpose of illustration inconnection with a carburetor of the down-draft type, the arrow in Figure2 indicating the direction of the flow of fluid through the carburetor.In all the figures, corresponding numbers are employed to indicate likeparts.

Referring to Figure 2, A generally designates a carburetor having a fuelmixture section B and a choke section C, the latter being ofconventional construction. Section B includes a conduit section I!defining a passageway or fuel conduit [2, section B being provided atits lower end with a flange 13 having lug [4 (Figure 3) thereon withsuitable apertures for fastening to an intake manifold (not shown) of aninternal combustion engine in customary manner.

Conduit H is fitted at its discharge or lower end with a venturi l5 ofconventional type, a fuel jet or nozzle l6 being mounted in the conduitwall at H with its slightly flared discharge end It positioned in thethroat of venturi l5 and its inlet end connecting with a passage l9formed in the wall of the carburetor.

Above jet [6, the conduit walls are apertured as at 2| to receive athrottle shaft 22 mounting a throttle valve 23, preferably of thebutterfly type. Above throttle valve 23 in choke section C is a chokevalve 24 of conventional type arranged to be operated in well knownmanner by conventional controls (shown in Fig. 5) such as a Bowden wire25 mounted on a bracket 26 and connected to a crank arm 21 on the chokevalve shaft. An air cleaner of conventional type (not shown) is providedabove choke section C so that the air entering the carburetor will berelatively free of dust and like impurities.

As viewed in Figure 2, throttle valve shaft 22 extends to the right andconnects with wellknown control means 28 (Figure 5) having an idlingadjustment assembly 29 associated therewith. At its left end (Figures 1and 2), shaft 22 extends into a float chamber 3|, preferably formedintegral with conduit section B. Float chamber 3| includes a lowersection 32 serving as a fuel reservoir and a cover section 33, thelatter being reduced at its top as at 34 (Figure 2) and merging into aconduit 35 leading into choke section C above choke valve 24. Thisinsures that the only air accessible to the top of the float chamber 3|must first pass through the air cleaner and be cleaned thereby.

As shown in Figure 1, float chamber 3| has a connection 36 for a fuelsupply conduit (not shown) leading from a suitable source of fuel, aconnecting nipple 31 being formed with a valve seat 38 and a valve guide39 to receive a needle valve 4| arranged to operate in a horizontalplane and control the entrance of fuel into the float chamber.

Needle valve 4| is preferably square or triangular in cross-section, asshown, to offer a minimum of resistance to the passage of fuel. An arm42 is pivoted for oscillation in float chamber 3! about a shaft 4.3, arm:2 being provided with an extension 44 positioned to engage the head ofneedle valve 4!. A pair of floats 45 and 46 are secured to the oppositeend of arm 42, the arm at this end being formed as a yoke with twoextending portions 41 and d8, each of which is secured to a float. Asshown in Figure 3, floats 45 and 46 are disposed symmetrically atopposite sides of the float chamber, and are spaced from the centerthereof whereby they tend to maintain the fuel level constant despitethe various angled positions assumed by the carburetor incident to itsuse on a motor vehicle. Floats l5 and 4B are connected together at theirouter ends by a brace member all.

By reason of a horizontal partition 49 and a vertical partition 5! inthe float chamber, the needle valve assembly is contained in a chamberthat is entirely filled with fuel at all times, this following becauseof the fuel level maintained on a line FL of Figure 1. This arrangementis unlike prior arrangements where it has been the practice to place theneedle valve and the chambar in which it operate in a vertical plane.Such prior devices have become filled partly with air and partly withfuel. As a result, any surge of the fuel in the direction of the needlevalve chamber permits the fuel to wash out from under the floats Whichfall and permit excess fuel to enter, while a surge in the oppositedirection or away from the needle valve chamber permits the fuel toagain influence the floats. The resultant operation is highlyunsatisfactory, particularly when such carburetors are used on vehiclesconstantly being displaced angularly, such as tractors and tanks.

In the construction herein disclosed wherein the needle valve chamber isalways sealed with liquid fuel, surge will not cause more fuel to enter,and under either normal or angular operation, no fuel can flow out (andbe replaced by air). Therefore, the floats 55 and 46 are the solecontrolling factors as to change of levels when the float chamber istipped and as the floats are concentric of the area of the floatchamber, they function to maintain a constant level at the center of thearea regardless of the angle of the chamber. As the metering arm (aswill be hereinafter explained) is at the central point or center ofconcentricity of the float chamber where the level is constant, itfollows that the fuel head effective on the metering arm will besubstantially constant. As all the fuel for all positions of operationis supplied by the metering arm, the carburetor will function correctlyat any angle up to the point where the fuel will flow b gravity over theupper edge of vertical partition 55, or the floats refuse to control theflow. The embodiment shown in Figure 1 will function correctly up to andincluding 60 percent grades.

Referring to Figure 2, throttle shaft 22 is provided with a cross boreor passage 52 connecting with passage IS in all operating positions ofthe shaft, and with a bore or passage 53 opening into the outerperiphery of the shaft at 5 A metering arm '55 is fixed, to throttlevalve shaft 22 at its left end in such a position that when the throttleis in fully closed position, arm 55 willbe in the position shown inFigure 1, and be held in such position by screw 56 entering the end ofshaft 22, and washer 57, which seals the end of the shaft 22. To permitready access to screw 56 and the end of shaft 22, the float chamber ispreferably bored and tapped at 58 and fitted with a screw plug 59.

Arm 55, shown in enlarged size in Figures 6 and '7, constitutes themetering means and is preferably made in two complemental halves 6| and62 arranged to be firmly fastened together by screws 63 or likefastening means and held in matched position by dowels 64 and 65. AnS-shaped conduit or groove 66 of semi-circular cross-section is cast orotherwise formed in each arm section (right and left shaped), so thatwhen halves and 62 are assembled, a passage, substantially circular incross-section, beginning at 61 and continuing in an S-shape is formed.The outlet end 68 of thi passage terminates with and aligns with passage54 in throttle valve shaft 22 (Figures 2 and '7).

Before assembling section halves SI and 52, a gasket 69 of fiber orsimilar material having the same general outline as arm 55 with all theholes therein required for assembly and of any desired thickness isplaced between the halves BI and 62. As will be noted in Figures 1 and6, a portion of gasket 69 corresponding to the outer periphery of arm 55is cut away, the cut-away section being represented by dotted line ll,12. and 13 in Figure 6. With such gasket 69 in place between the armsections, and the sections firmly secured together, a portion of the S-shaped passage formed in the arm 55 is in communication with theatmosphere above the fuel level in the float chamber by a slot 14(Figures 1, 2, and 7), this slot being of a width corresponding to thethickness of gasket 69. By varying the thickness of gasket 59, the Widthof slot 14 can be readily varied. This provides an easy and cheap meansof adjustment which does not require any extensive machining ormutilation of the parts so that they cannot be returned to theiroriginal adjustment.

The length of that portion of the S-shaped passage in the arm exposed toatmosphere (in the position shown in Figure 1) is represented by thearea between lines 1! and 73, where the gasket has been cut away.Obviously the length of this slot can be easily varied by varying theextent to which the gasket is cut away, i. e., the positions of lines Hand 13.

While the S-shaped hole formed between the section halves SI and 62 willbe circular in crosssection between lines H and 13, it is formed as twohalf-circular holes, one-half on each side of gasket 69, after passingline 13, as shown at 15 and 16 (Figure '7) and such half holes continueuntil connection is made with the throttle shaft passage 54.

The metering arm 55, above described, is possessed of a number ofadvantages in its operation in that its shape with respect to its entryinto the liquid fuel prevents over correction at closed, or nearlyclosed, positions of the throttle, while in the other positions, itoperates to automatically correct the mixture to insure the feed of thecorrect air fuel ratios to the carburetor conduit.

As shown in Figure 1, vertical partition 5| extends upwardly to a pointwhere it terminates adjacent the curved underside of arm 55. The upperpart of the partition therefore acts as a fence or seal in combinationwith the inside curve of arm 55 to prevent fuel from the float chamberreaching a point adjacent the throttle valve shaft and the connection ofarm 55 thereto,

whereby the possibility of liquid fuel being drawn in'to'the carburetorconduit around the bearing and connections to the throttle valve shaftand upsetting the mixture is eliminated.

To further insure correct operation of metering arm 55 and to furtherprotect against the ill effects of changes in the fuel level in thefloat chamber, indicated in Figure 1 by dotted line FL, a fiber orBakelite block 11 having a curved inner face 18 of channel shape and ofthe same curvature as the slotted periphery of arm 55 is arranged to beresiliently held against the slotted face of arm 55 and rigidly held invertically adjustable position as shown in Figure 1. In the positiontherein shown, where arm 55 is in a position corresponding to idling orclosed throttle position, a small portion of the slot in arm 55 is belowblock '17 in the liquid fuel, while the balance of the slot above blockH is open to air. As block 1! is positioned so that fuel level line FLpasses substantially through the center thereof, it is obvious that thefuel level may rise and fall to a considerable extent without alteringthe portions of slot 14 that are exposed to fuel and air and withoutchanging the air-fuel ratio at the position shown.

In this idling position, it will be noted that the lower loop of theS-shaped passage 66 is above fuel level line FL. This is important undersome conditions. For instance, in re-starting a warm engine, if the loopbe below fuel level line FL, the air will be valved off entirely. Thiswould cause the engine, while being cranked, to go too rich at theidling position where the air-fuel ratio is always touchy, so that theengine would refuse to start. With the arrangement herein disclosed,this valving off of fuel can be delayed to any desired throttle positionwhen the engine is not as touchy as at idling, the control being theposition of the lower loop of passage 66 as regards fuel level at theidling position.

With reference to Figure 1, it is apparent that upon opening thethrottle from closed to open position, arm 55 will rotate in acounter-clockwise direction and be progressively immersed in the liquidfuel. Such movement will immediately increase the proportion of the slotbelow block 11, and therefore increase the amount of fuel fed by the arm55. At the same time, such movement will decrease the proportion of theslot above block 1'! and proportionately diminish the amount of airadmitted to the passage in the arm. Both operations tend to enrich theamount of fuel in direct proportion to the degree of opening of thethrottle.

It is also to be noted that if a degree throttle valve be used, i. e., athrottle valve which when closed is diametrically positioned across thecarburetor conduit, arm 55 would move relatively rapidly in going from aposition corresponding to closed throttle position to a positioncorresponding to open throttle position as regards the amount of spacemade available for the passage of air through carburetor conduit I2 bysuch a 90 degree throttle. If a 70 degree throttle be used (a throttlevalve which is 20 degrees away from a diameter when in closed position),the same relative movement of arm 55 would open a considerably greaterspace for the passage of air through carburetor conduit I2. From thisobservation, it is apparentthat with no other change than the angle ofthe throttle in closed position, any desired change in throttleprogression can be made.

When the thottle valve is in fully open posi tion, slot M will beentirely beneath fuel level line FL. At heavy loads and low enginespeeds, the fuel would tend to syphon from the float chamber to the fueljet which flow might be greatly in excess of engine requirements. Or ifthe engine be shut off in wide open throttle position, the liquid fuelwould also continue to flow by syphon action even though the engine isnot running. To prevent such occurrences, a jet i9 is placed in thes-shaped passage (Figures 1 and 6) at a point where it can function toprevent such a syphon action and also perform as a mixture control jet,as will be later described. It has also been found desirable to place anauxiliary air jet 8! in the extreme end of the S- shaped passage 66 inarm 55 (Figures 1 and 6) where it will always be above fuel level lineFL even though the throttle be in wide open position.

It has been found possible without changing the width of slot 14 in arm55 to vary the airfuel ratio by a trade of values between jets "I9 andti. For instance, with a slot 14 having a width of 0.010 inch and ananti-Syphon jet 19 having a diameter of 0.022 inch, the mixture at wideopen throttle and below 30 miles per hour can be enriched bysubstituting an 0.020 inch diameter anti-syphon jet 19. At speeds above30 miles per hour, it has been possible to vary the mixture withoutdisturbing the slot width by changing the diameter of jet 3!. The latterchange will not influence the change in antisyphon jet Z9 and the changein the anti-syphon jet will but little influence the latter.

On some engines, it has been found that the fuel requirements in goingfrom one throttle position to another are not uniform and somemodification of the straight or uniformly wide slot I is required. Thisproblem is readily solved by milling a cut of any desired width or depthon the inside face of one or both of the arm halves iii and 62. Or anextra cut in the gasket 69 may be made in advance of dotted line 't'i(Fig. 6) which extra cut acts as a power jet when the correspondingposition of the throttle is reached and gives the added fuel necessaryfor the added power which the throttle position indicates is required.

A further control of the air fuel ratios delivered by metering arm 55 inoperation is found in the length of block 'i'! which is illustrated inFigure l as of minimum length. For instance, by increasing the length ofblock Ti above fuel ievel line FL, the air entering slot 14 in arm 55 ismetered off that much sooner while leaving the total liquid fuel flowarea below the block as before.

The above described assembly sets up three stages of control as regardsthrottle progression.

The first resides in the angle of the throttle selected in the closedposition which controls the rate of opening of the available air flowpassage in the carburetor conduit as the throttle is opened. This fuelcontrol covers a range up to approximately 1,000 R. P. M. light load.

The second control resides in the selection of the length of block 11which controls the fuel flow in relation to throttle movement up toapproximately 2,500 R. P. M. light load.

The third control resides in the thickness of gasket 69 which determinesthe width of slot 14. While a change in slot width is naturallyrefiected in all stages of control, it is most important in the finalstage, or between 2,500 R. P. M. and wide open position.

The three aforementioned controls plus the anti-syplion jet 79 and theair bleed 5i establish a control for the entire range of throttleprogression and for any variation in loads or R. P. M. of the engine atany throttle position.

Still a further control is available in the ability to make slot 14 ofnon-uniform width and to correlate the portions of different width withcorresponding throttle positions.

It is important that block 11 be mounted in a manner whereby no wear candevelop that would tend to permit it to oscillate in a vertical plane.In the present invention, this is accomplished by providing a taperedmetallic button 82 integral with block H. A. spring wire member 83 witha loop at both ends is provided, the upper loop of member 83 beingfulcrumed about a pin 84 in a manner whereby spring member 83 can swingsideways to allow for variations in the position of float chamber cover33, and other manufacturing errors, while the lower loop fits overtapered button 82 on block Ti. As shown in Figure 1, member 83 functionsto firmly urge block 71 to the right against the periphery of arm 55. Ifwear develops between the lower loop on member 83 and button 82. theloop merely moves to the right on the tapered portion of the button. Inthis manner, the loop can be depended upon to hold the block in itsselected position at all times.

Pin 84 and the upper loop of spring member 83 are contained within ahollow boss 85 formed in cover 3| of the float chamber, the inner bore86 of boss 85 at its upper end being square or noncircular incross-section to receive a tubular-like member 87 of correspondingcross-sectional shape. Such shaping permits longitudinal movement ofmember 87 in the hollow boss, but prevents rotation. A stud 88 is fixedto the upper end of member 87. A nut 89 is threaded to stud 88- wherebyon rotation of nut 89, member 81 can be vertically adjusted to effect alike adjustment of block 71. Serrations 9! on the upper surface of theboss and the lower face of the nut prevent the nut from vibrating fromits adjusted position.

A compression spring 52 is provided in member Bl in combination with aplug 93 to keep the upper loop of spring member 83 firmly down againstits fulcrum pivot 84 and prevent any vertical movement thereof.

The lower part of boss 85 is enlarged to receive a relatively heavycompression spring 94 which reacts against flange 95 on member 81 andshoulder 95 inside the hollow boss to strongly urge the entire springsupporting assembly downward.

As shown in Figure 1, fuel level line FL passes through the center ofbutton 82 on block Ti and in the relation shown, the fuel level may riseor fall as much as without any appreciable effect on the air fuel ratiodeveloped by arm 55. In Figure 1, only a small portion of slot M isexposed to fuel below block ll. In this position, which is the closedthrottle or idling position, if an adjustment of the fuel ratios isrequired, block Ti may be raised by turning nut 89 to expose more ofslot 74 to the fuel to enrich the mixture. If it is desired to lean themixture, block ll may be lowered, and the amount of slot M exposed toliquid level be shortened.

To provide for injecting fuel into the carburetor conduit when rapidacceleration is desired, a pump cylinder 91 is formed in the bottom offloat chamber 3!, cylinder 91 having an apertured piston 58 thereincarrying a check valve 99 of conventional type whereby fuel is free topass down throughthe piston but=n t upwardly.

Referring to Figures 1 and 3,, a connecting link IOI formed of springwire isattached to metering arm 55 by a pin or screw I02 and do the topof piston 98 by a pin or screw I03. Upon sudden opening movement of jthe carburetor throttle, the link IOI is distorted and loaded. Inreturning to its original shape, it forces piston 95 downwardly to pumpa sustained charge of fuel out of cylinder 91 through a discharge portI04 connected by a conduit (not shown) to a boss I05 (Figure 5), and adischarge jet I06 (Figures 2 and 5). In this connection, check valves(not shown) are used as in conventional practice.

In Figure 5, a boss I! is shown provided with a tapped bore I08 and anaperture I09 drilled just above throttle valve 23 when the latter is inclosed or idling position to provide the desired spark controlconnection which functions in well known manner.

Figures 9, l0, and 11 illustrate a modified form of block and adjustmentmeans for the metering arm 55 which provides a less sensitive idlingmixture and adjustment means than hitherto described, and isparticularly adapted for providing cheap and accurate means forcontrolling airfuel ratios at throttle positions just above idlingposition and for as long or as short a period in the opening phase ofthe throttle as different makes of engines may require. Different makesof engines have different requirements just above idling position, whichrequirements extend over different periods for each type of engine. Thishas been a difficult problem in the automobile industry and attemptshave been made in the past to solve it by some devices as idling jetshaving openings of peculiar shapes and idling jets provided incombination with so-called second holes having adjustable means incombination therewith.

In solving this particular problem in a cheap and reliable manner, ametering arm 55 of the same construction as hitherto described is used,except that gasket 69 is provided with an angular cut H4 which it isunderstood may be varied in both angle and position for different typesof engines. This metering arm is employed in combination with anadjustable block 11' (Figs. 9, l0, and 11). Block 11 difiers from blockT! of Fig. 1 in that it is formed with two grooves III and H2 separatedby a solid portion or neck H3 extending into contact with the curvededge of metering arm 55. The portion of block 11' above neck H3, inwhich groove III is formed, extends sufficiently far above the fuellevel line so that fuel will not be surged and splashed into it whilethe portion of block TI in which groove H2 is formed extendssufiiciently far below the fuel level line to insure against any surgeor splashing of the fuel uncovering the groove.

The lower end of groove I I I terminates just below fuel level. line atneck I I3 which acts as a seal between groove III and groove H2, neck H3being of predetermined length, as determined by the characteristics ofthe engine upon which the carburetor is to be used.

A hole H is formed in neck H3 connecting with the slot in the edge ofthe metering arm, as shown in Fig. 9, a second hole I It, metered, beingdrilled between the lower end of groove III and hole H5.

In operation with the engine running, groove I I2 is always full ofliquid fuel, and according to the adjustment made at idling position(the position shown in Fig. 9), a small portion of the slot in the edgeof metering arm 55, determined by th thickness of gasket 69 and theangle of cut H4, is exposed to liquid fuel. At the same time hole I I5straddles or caps the slot in the metering arm at a point above thepoint of access of the liquid fuel and between the liquid fuel and thelow pressure area in the metering slot. By metering hole H6, whichconnects hole II5 to atmosphere, any desired pressure can be maintainedin the metering slot at the point immediately adjacent hole I I5. Thisarrangement eliminates the necessity of using any small openings coupledwith relatively large pressure differentials, which openings aredifl'icult to maintain in service, and enables any desired amount of theslot provided by cut-away portion I of gasket 69 to be exposed to grooveII2, while eliminating all sensitiveness in the adjustment of the fuelfed in the idling or closed throttle position.

As the metering arm rotates counter-clockwise (as viewed in Fig. 9)corresponding to opening movement of the throttle, a greater length anddepth of the metering slot is exposed to groove II2 as well as to agreater depth of fuel.

Difierent makes or types of engines have substantially different fuelrequirements, particularly between idling R. P. M. and 1000-4200 R. P.M. In the present invention, these requirements are easily and cheaplymet by varying the angle and extent of cut of gasket 69 at t, the shapeand length of the out being capable of any variation. All theundesirable sensitivity incident to conventional idling adjustments iseliminated by the admission of air through holes H5 and lit, thethrottle progression (which at this phase of operation really means theair fuel ratio at the touchy point just off idling) is controlled by nomore eX- pensive means than a cut of predetermined shape in a gasketmade of fiber, or like material.

It is to be understood that the invention may be embodied in specificforms other than that illustrated without departing from the principleor essential characteristics thereof. The embodiments shown aretherefore to be considered as illustrative and not restrictive, thescope of the invention being defined by the appended claims rather thanthe foregoing description and drawings. All modifications and changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be included therein.

We claim:

1. A carburetor for an internal combustion engine comprising a conduit,a throttle valve in said conduit, a float chamber, a fuel jet in saidconduit, and means to conduct and meter fuel to said fuel jet from saidfloat chamber comprising a slotted member arranged to be progressivelyimmersed in the fuel in said float chamber as said throttle valve movesfrom closed to open position,

means to seal the portion of said slot immediately adjacent the fuellevel line in said float chamber in all positions of said slottedmember, and means to control the pressure in said slot adjacent aid fuellevel line.

2. The combination claimed in claim 1 wherein duit, and means to'cond'uctand meter iuel to said fuel jet from "said floatchambercomprising a slotted member 1 arranged to be progressivelyimmersed in the fnel'in said float-chamber as said throttle valve movesfrom closed to open position, and meansto seal the portion-ofsaid slotimmediately adjacent the "zfuel level line in said 'float chambercomprising a. block having a groove therein substantially parallel tosaid slot, and means in said groove in sealing relation with-said slotto divide said groove into a section below the fuel level line-and asection extending above vthe fuel level line to the atmosphere in saidfloat chamber.

4. The combination claimed in claim 3 wherein said sealing means isconnected to said upper groove through a metered aperture.

5. Aearburetor"ior-an intemal combustion engine-comprising a conduit, athrottle valve in said 'conduiwa fioat chamber, aiuel jetin saidconduit, andmeans to'conduc't and meter fuelto said "fuel

